Coherent properties of a tunable low-energy electron-matter-wave source

Abstract

A general challenge in various quantum experiments and applications is to develop suitable sources for coherent particles. In particular, recent progress in microscopy, interferometry, metrology, decoherence measurements and chip based applications rely on intensive, tunable, coherent sources for free low energy electron matter waves. In most cases, the electrons get field emitted from a metal nanotip where its radius and geometry towards a counter electrode determines the field distribution and the emission voltage. A higher emission is often connected to faster electrons with smaller de Broglie wavelengths, requiring larger pattern magnification after matter wave diffraction or interferometry. This can be prevented with a well-known setup consisting of two counter electrodes that allow independent setting of the beam intensity and velocity. However, it needs to be tested if the coherent properties of such a source are preserved after the acceleration and deceleration of the electrons. Here, we study the coherence of the beam in a biprism interferometer with a single atom tip electron field emitter if the particle velocity and wavelength varies after emission. With a Wien filter measurement and a contrast correlation analysis we demonstrate that the intensity of the source at a certain particle wavelength can be enhanced up to a factor of 33 without changing the transverse and longitudinal coherence of the electron beam. In addition, the energy width of the single atom tip emitter was measured to be 377 meV, corresponding to a longitudinal coherence length of 82 nm. The design has potential applications in interferometry, microscopy and sensor technology.

Information transfer by quantum matterwave modulation

“…Thus, 4000 to 5000 counts/s were accumulated on the whole screen, resulting in 1000 to 1500 counts/s for each recorded interference pattern within five fringes. It is sufficient signal to determine the fit parameters and the contrast with a reasonable accuracy as described in the methods [24,28]. The extracted interference contrast is plotted by the blue curve in Fig.…”

“…It includes several beam optic components from a former experiment by Sonnentag et al [37]. A single atom nanotip field emitter [22,[26][27][28] is the origin of coherent electron waves. The beam is guided by two electrostatic deflectors to illuminate the biprism.…”

“…We apply the Wien filter to shift the wave packets of the separated beam paths as described in detail in [28,30]. The Wien filter introduces a longitudinal shift of ∆y = L ∆x U W F 2 D Utip , where L is the length of the Wien filter deflector plates, ±U W F the applied voltage, D is the distance between them and U tip the electron acceleration voltage [28].…”

“…The matterwaves of electrons in a biprism inter-ferometer [9,[20][21][22][23][24][25] are used as the carrier waves to be modulated for signal transmission. The coherent electron beam is generated by a nanotip field emitter [26][27][28] and separated by a biprism fiber into two partial waves. After superposition by a quadrupole lens, an interference fringe pattern is formed on a delay line detector with a high spatial and temporal resolution [29].…”

A Scanning 2-Grating Free Electron Mach-Zehnder Interferometer

“…Electron holography and interferometry can enable nanoscale phase imaging [1,2], the exploration of the Aharonov-Bohm effect [3,4], interaction-free measurements and quantum electron microscopy [5][6][7], the measurement of coherence properties [8][9][10], quantum state tomography [11,12], and the coherent control of the free electron wavefunction [13]. While interferometry is widely used in optics and photonics fields such as astronomy [14], optical metrology [15], and quantum optics [16], electron interferometry has advanced at a slower pace, partially due to a lack of basic optical elements such as beamsplitters and mirrors that can be used to build a versatile system.…”